1. Field of the Invention
The present invention relates to a tape cartridge, and more particularly to a tape cartridge comprising a magnetic shielding plate disposed at the inner part of a head insertion window defined at a front face of the cartridge.
2. Description of the Prior Art
An example of a conventional magnetic shielding plate is shown in FIG. 1 and FIG. 2, wherein a head insertion window 6 is defined on a front wall of a case body 1 which is formed by a top half 1a and bottom half 1b and a magnetic shielding plate 10 is situated inside the head insertion window 6 standing in a vertical attitude. The magnetic shielding plate 10 is inserted in a gap between a rib 34 and bosses 33 (only one is shown in FIG. 1) projected from the inner surface of the top half 1a and bottom half 1b, with respective top and bottom edges fitted in slots 23 defined in the respective inner surfaces of the top and bottom halves 1a and 1b. Also, a pad supporting spring 11 having a pad 15 is supported in front of the magnetic shielding plate 10.
In order to facilitate insertion of the magnetic shielding plate 10 in the slots 23 and the gap between the ribs 34 and the bosses 33, the widths of the slot and the gap are defined slightly greater than the thickness of the magnetic shielding plate 10. Therefore, in the process of assembling the top half 1a on the bottom half 1b after mounting of the magnetic shielding plate 10 in the bottom half 1b, the magnetic shielding plate 10 rattles in the bottom half 1b and the rattling causes the pad supporting spring 11 to be displaced. In addition, since there is such a condition that the magnetic shielding plate 10 rattles between the top and bottom halves 1a and 1b after assembling of them is completed, when the tape cartridge is mounted in a cassette radio or car stereo, the magnetic shielding plate rattles due to the vibration of a tapedeck of the cassette radio or car stereo and rattling of the magnetic shielding plate 10 in the case body 1 causes the case body to be vibrate slightly, resulting in a bad effect of on the tape running characteristic.
In order to eliminate the problem of the rattling of the magnetic shielding plate 10, there has been proposed to provide a supporting member, as shown in FIGS. 3 and 4 as disclosed in the Japanese Utility Model laid open No. 52-77730. The proposed arrangement is such that there is provided a pair of projections 35 at the left and right portions of the front wall 23a defining the slot 23 of either one of the slots of the top half 1a or bottom half 1b. Each of the projections 35 is so rounded shown at 35a that the projection is expanded toward the mount of the slot 23 so as to secure the magnetic shielding plate 10 by the projections 35, the rear wall 23b of the slot 23 and bosses 33 formed behind the slot 23.
In the arrangement shown in FIGS., 3 and 4, it is still difficult to completely eliminate the rattling of the magnetic shielding plate 10 partly because the slot 23 is rather shallow and partly because the force of the round portions 35a pressing on the magnetic shielding plate 10 is small as the magnetic shielding plate is pressed only by a part of the round portion 35a of the projection 35 formed in the shallow slot. Originally the thickness of the portion of the case body 1 where the slot is formed is thin, about 1 mm, and the depth of the slot 23 formed in the thin portion has to be shallow. Accordingly, even if the projection 35 is formed over the full height of the front wall 23a of the shallow slot 23, the size of the projections 35 has to be insufficient to support the magnetic shielding plate 10 having a 10 mm height which is several times the height of the projections. In addition, the projection is formed in the round shape, as shown at 35a, which can not function to fully press the magnetic shielding plate 10. Therefore, the proposed arrangement also has such a problem as mentioned below in the process of assembling of the top half 1a to the bottom half 1b after mounting of the magnetic shielding plate 10 in the bottom half 1b. As mentioned above, it is difficult to secure the magnetic shielding plate 10 stably by only pressing the magnetic shielding plate by the round projections 35a. Moreover, according to the proposed arrangement, the magnetic shielding plate 10 is apt to fall frontward when the case body 1 is subjected to vibration in the assembly line in the manufacturing process, partly because the round portions 35a engage with only the front face of the magnetic shielding plate 10, allowing frontward falling thereof, and partly because the pad supporting spring 11 is easily displaced, therefore there still remains problems to be solved.